JP5118720B2 - Manufacturing method of shape memory alloy coil spring - Google Patents

Description

  The present invention relates to a method of manufacturing a shape memory alloy coil spring, and more particularly, to a method of manufacturing a shape memory alloy coil spring having a small coil diameter by twisting the shape memory alloy coil spring to reduce the diameter of the coil spring.

  A shape memory alloy has a martensite phase below a certain transition temperature and may deform in shape, but after such deformation occurs, if the temperature rises above the transition temperature, it changes to an austenite phase. It is a material that has the property of returning to its original shape when a phase transition occurs. Such shape memory alloys are usefully used in various fields.

  Shape memory alloy elements are most often applied in the field of coil springs because they can cause large displacements. As one example, a 30 mm long wire recovers by 1% and produces a displacement of 0.3 mm, while a coil spring having a coil diameter of 8 mm, a wire diameter of 1 mm, and a winding number of 30 produces a displacement of 50 mm.

  The shape of a general metal coil spring is formed simply by winding a coil. On the other hand, the shape memory alloy coil spring is formed in a complete shape by heat-treating the wound coil. In general, there are two methods for manufacturing a shape memory alloy coil spring.

  One method (hereinafter referred to as method A) is a method in which a shape memory alloy wire is wound around a rod having a predetermined diameter and fixed, and then heat-treated at an appropriate temperature in order to memorize the shape.

  The other method (hereinafter referred to as method B) is a method in which a coil spring is manufactured industrially using a wire processing machine and then heat-treated, but this method may cause the coil spring to unwind and increase its diameter. Because there is, you have to be careful. The shape of the final coil spring is the shape at the time of heat treatment, but a shape memory treatment is usually possible at 250 ° C. or higher. In practice, since shape memory and superelastic behavior vary greatly depending on the heat treatment temperature, it is generally performed at about 250 to 600 ° C. depending on the purpose.

  Recently, application of shape memory alloy springs to many electric products such as mobile phones has been attempted. Because the spring installation space is small for miniaturization of the product, the coil diameter must be small. Moreover, in order to exhibit an appropriate spring constant, it is necessary to use a moderately thick wire, so the numerical value of wire diameter / coil diameter (d / D) increases. The coil diameter is defined as a coil inner diameter, a coil outer diameter, or a coil average diameter. Generally, an average diameter that is an intermediate value between the inner diameter and the outer diameter is adopted, but in this specification, the outer diameter is meant for convenience.

  By the way, since shape memory alloys are very elastic, it is difficult to manufacture a coil spring having a large value of wire diameter / coil outer diameter (d / D). In the shape memory alloy coil spring, 1/5 to 1/6 is the limit of the value of the wire diameter / coil outer diameter that can be generally manufactured. However, in order to reduce the size of the product, a quarter or more coil spring is often required.

  As an example, it is assumed that the space in which the spring can be installed is 1.5 mm and a coil spring that can exert a force of 3N is required. The allowable coil outer diameter needs to be about 1.45 mm, and in order to exert a force of about 3 N, a coil spring having a wire diameter of 0.35 mm must be manufactured in the case of Ni-Ti alloy. When manufacturing a Ni-Ti coil spring having a wire diameter of 0.35 mm and a coil outer diameter of 1.45 mm, the following problems occur when a conventional method is employed. When the above-mentioned method A is adopted, a wire having a diameter of 0.35 mm must be wound around a rod having a diameter of 0.75 mm, fixed, and heat-treated, but this is practically impossible. Therefore, in the method A, it is difficult to manufacture a small coil spring. Also in Method B, the coil outer diameter that can be manufactured with a wire having a diameter of 0.35 mm is 1.85 to 2.05 mm, and thus it is impossible to manufacture a coil spring having a required coil diameter.

  The present invention is for solving the above-mentioned problems, and a manufacturing method of a shape memory alloy coil spring having a small coil diameter, that is, a coil diameter is small and a value of wire diameter / coil diameter (d / D) is large. It aims at providing the manufacturing method of a shape memory alloy coil spring.

In order to achieve such an object, a method of manufacturing a shape memory alloy coil spring according to the present invention includes a step of manufacturing a coil spring, and a reduction in which the coil diameter is reduced by rotating the both ends of the coil spring to impart torsional deformation. After the diameter stage and the diameter reducing stage are finished, a pitch adjusting stage for adjusting a pitch of the coil spring by adjusting a distance between both ends of the coil spring, and a shape memory heat treatment for the coil spring after the pitch adjusting stage. And a heat treatment step to be performed.

  The diameter reduction step includes a fixing step of fixing both ends of the coil spring using two grips and a rotation step of rotating the two grips.

  With such a configuration, after a coil spring having a small coil diameter is manufactured, both ends of the coil spring are rotated to impart torsional deformation to further reduce the coil diameter.

  The grip may have a cylindrical shape or a columnar shape in which a spiral groove is formed on the outer peripheral surface.

  In the fixing step, both ends of the coil spring may be inserted into the spiral groove and fixed.

  Further, the diameter reduction step and the heat treatment step may be repeated a plurality of times.

Furthermore, the method of manufacturing a shape memory alloy coil spring according to the present invention includes a fixing step of fixing both ends of the coil spring using two grips, and twisting the coil spring by rotating the two grips in opposite directions. a reduced diameter step to reduce the coil diameter giving deformation, after the diameter reduction step is completed, the pitch adjustment step of adjusting the pitch of the coil spring by adjusting the distance between both ends of the coil spring, the pitch adjustment A heat treatment step of performing a shape memory heat treatment on the coil spring that has undergone the steps .

Further, according to the method of manufacturing a shape memory alloy coil spring of the present invention, both ends of the coil spring are inserted into the first pipe, a wedge-shaped second pipe is inserted between the first pipe and the coil spring, and the coil spring is inserted. A fixing stage for fixing both ends of the coil, a diameter reducing stage for reducing the coil diameter by twisting the coil spring by rotating the first pipe, and a gap between both ends of the coil spring after the diameter reducing stage is completed. And adjusting the pitch of the coil spring to adjust the pitch of the coil spring, and a heat treatment step of performing shape memory heat treatment on the coil spring that has undergone the pitch adjustment step .

  The diameter reduction step, the pitch adjustment step, and the heat treatment step may be repeated a plurality of times.

Furthermore, the manufacturing method of the shape memory alloy coil spring of the present invention includes a fixing step of fixing both ends of the coil spring using two grips, and a step of inserting a straight wire or a rod-like member inside the coil spring. A diameter reducing step for reducing the coil diameter by twisting the coil spring by rotating two grips in opposite directions, and after the diameter reducing step is completed, an interval between both ends of the coil spring is adjusted. A pitch adjusting step of adjusting the pitch of the coil spring, and a heat treatment step of performing a shape memory heat treatment on the coil spring that has undergone the pitch adjusting step .

  Here, a plurality of the straight wires may be arranged inside the coil spring.

  The straight wire may be positioned on a circumference having a diameter corresponding to a final inner diameter of the coil spring in order to determine a diameter reduction range of the coil spring in the diameter reduction step.

  According to the present invention, a shape memory alloy coil spring having a small coil diameter and a large value of wire diameter / coil diameter (d / D) can be easily manufactured.

It is a perspective view which shows the coil spring and grip by one Embodiment of this invention. It is a figure which shows the state by which the grip was fastened by the both ends of the coil spring of FIG. It is a figure which shows the state by which the grip of FIG. 2 rotated and the diameter of the coil spring was reduced. It is a figure which shows the state by which the pitch of the coil spring was adjusted by adjusting the space | interval of a grip. It is a perspective view which shows the shape memory alloy coil spring manufactured by one Embodiment of this invention. It is a figure which shows the state provided with the wire inside the coil spring by other embodiment of this invention. It is a figure which shows the state from which the diameter of the coil spring was reduced from the state of FIG. 6, and the pitch was adjusted. It is a figure which shows the state which provided the rod-shaped member instead of the wire inside the coil spring, and reduced the diameter. It is a figure which shows the state from which the diameter of the coil spring was reduced from the state of FIG. 8, and the pitch was adjusted. It is a figure which shows the state which fixes both ends of a coil spring using the 1st and 2nd pipe by further another embodiment of this invention.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view showing a coil spring and a grip according to an embodiment of the present invention, FIG. 2 is a view showing a state where grips are fastened to both ends of the coil spring of FIG. 1, and FIG. 2 is a diagram illustrating a state where the grip of FIG. 2 is rotated and the diameter of the coil spring is reduced, and FIG. 4 is a diagram illustrating a state where the pitch of the coil spring is adjusted by adjusting the gap between the grips. FIG. 5 is a perspective view showing a shape memory alloy coil spring manufactured according to an embodiment of the present invention.

  As shown in FIG. 1, first, a coil spring 10 is manufactured by using a shape memory alloy so that the coil diameter is temporarily minimized. The coil spring 10 is manufactured by a normal manufacturing method, and considering that the coil spring has a small coil diameter, the coil spring 10 is preferably manufactured by using the method B among the conventional spring manufacturing methods described above. This stage is called the manufacturing stage.

  Both ends of the coil spring 10 thus manufactured are fixed using the grips 20 and 30. The grips 20 and 30 have a cylindrical shape having a predetermined length, and two grips 20 and 30 are provided to fix both ends of the coil spring 10. Further, spiral grooves 22 and 32 are formed on the outer peripheral surfaces of the grips 20 and 30, and when the coil spring 10 is fixed to the grips 20 and 30, both ends of the coil spring 10 are connected to the spiral grooves 22 and 32. Wind around and fix. FIG. 2 shows a state in which the grips 20 and 30 are fixed to both ends of the coil spring 10. The grips 20 and 30 may be cylindrical.

  Thereafter, as shown in FIG. 3, when the two grips 20 and 30 are turned in opposite directions, the number of turns of the coil spring 10 increases and the outer diameter of the coil spring 10 naturally decreases. This stage is called a diameter reduction stage. Here, the number of rotations of the grips 20 and 30 is set to a number necessary for obtaining a desired coil diameter.

  Further, when a desired coil diameter is obtained, it is necessary to adjust the pitch of the coil spring 10, and this is achieved by adjusting the distance between the two grips 20 and 30 as shown in FIG. . In general, the pitches are adjusted so that the lengths of the coil springs 10 become longer by pulling the grips 20 and 30 fixed to both ends of the coil springs 10 in a direction away from each other. This stage is called a pitch adjustment stage.

  Thereafter, shape memory heat treatment is performed on the coil spring 10. After adjusting the pitch of the coil spring 10, if shape memory heat treatment is performed with the grips 20 and 30 fixed to both ends of the coil spring 10, the coil spring 10 having the coil diameter and pitch during heat treatment can be obtained. it can. The shape memory heat treatment is performed by an ordinary method, and the details thereof are omitted in the present invention. This stage is called a heat treatment stage.

  FIG. 5 shows a shape memory alloy coil spring 10 having a reduced coil diameter, completed through the above-described steps.

  However, if the coil diameter is excessively reduced at once, the coil spring may be distorted or not smooth. In order to prevent this, it is possible to gradually reduce the coil diameter by repeatedly reducing the coil diameter and performing the heat treatment after performing the shape memory heat treatment. Alternatively, the coil diameter reduction step, the pitch adjustment step, and the heat treatment step may be repeated in order to greatly reduce the coil diameter and obtain a desired pitch.

6 and 7 show another embodiment of the present invention.
In the figure, in order to improve the straightness of the coil spring 10 and obtain a uniform coil diameter, a method of inserting and penetrating straight wires 40 and 50 into the coil spring 10 is shown. Here, the positions of the wires 40 and 50 in the coil spring 10 are preferably on a circumference having a diameter corresponding to the final inner diameter of the coil spring 10 having a reduced diameter. That is, it is possible to determine the range of diameter reduction until the final inner diameter where the inner diameter of the coil spring 10 is reduced at the diameter reduction stage so that the inner diameter of the coil spring 10 is in contact with the straight wires 40 and 50 and the inner diameter is not further reduced.

  FIG. 6 shows a state in which cylindrical grips 20 and 30 are fixed to both ends of the coil spring 10 and straight wires 40 and 50 are provided through the inside of the coil spring 10 and the grips 20 and 30. Further, FIG. 7 adjusts the pitch of the coil spring 10 by adjusting the diameter reduction step for reducing the coil diameter of the coil spring 10 and the grip interval by rotating the grips 20 and 30 in opposite directions in the state of FIG. The coil spring which passed through the pitch adjustment step is shown.

  In the present embodiment, the method in which the two wires 40 and 50 are arranged at equal intervals in order to improve the straightness of the coil spring 10 has been shown, but the present invention is not limited to this and is necessary. Accordingly, 3 to 4 wires may be arranged at equal intervals. Moreover, you may use the pipe or bar which has a small diameter which can be inserted and penetrated inside the coil spring 10 and the grips 20 and 30 instead of a wire.

  FIGS. 8 and 9 show a method of manufacturing the coil spring 10 by inserting and penetrating a rod-like member 55 in order to improve the straightness of the coil spring 10 and to obtain a uniform coil diameter. Here, the outer diameter of the rod-shaped member 55 is preferably equal to the final inner diameter of the reduced coil spring 10. That is, the coil spring 10 is completed when the inner diameter of the coil spring 10 is reduced at the diameter reduction stage and the inner diameter is in contact with the rod-shaped member 55 so that the inner diameter is not reduced.

  9, the grips 20 and 30 are rotated in opposite directions in the state of FIG. 8 to adjust the diameter reduction step for reducing the coil diameter of the coil spring 10 and the grip interval to adjust the pitch of the coil spring 10. The state after the pitch adjustment stage is shown.

  FIG. 10 illustrates a method for reducing the coil diameter of a coil spring according to still another embodiment of the present invention. In the figure, first pipes 60 and 70 having outer diameters larger than the outer diameters at both ends of the coil spring 10 are provided, and both ends of the coil spring 10 are inserted into the first pipes 60 and 70 by a certain length. Further, wedge-shaped second pipes 65 and 75 are inserted and fixed between the coil spring 10 and the first pipes 60 and 70. In this way, the first pipes 60 and 70, the second pipes 65 and 75, and the coil spring 10 are coupled and fixed so that they can rotate integrally. In this state, when the two first pipes 60 and 70 are rotated in opposite directions, both ends of the coil spring 10 rotate together with the first pipes 60 and 70 to cause torsional deformation of the coil spring 10, resulting in the coil diameter being reduced. The pitch of the coil spring 10 can be adjusted by reducing and adjusting the interval between the first pipes 60 and 70. Thereafter, the shape memory heat treatment step is performed as in the above-described embodiment.

Hereinafter, specific examples to which the present invention is applied will be described.
If an electronic communication product requires a 3N compression spring with a thickness of less than 1.5 mm, the calculation results in a Ni-Ti alloy spring with a wire diameter of 0.35 mm, a coil outer diameter of 1.45 mm, and a pitch of 1.0 mm. is necessary. If a general metal, for example, a stainless spring is used, plastic deformation occurs and cannot be applied.

  As a specific example to which the method of the present invention was applied, first, a wire having an alloy composition of 50.8Ni-Ti (atomic ratio) and a diameter of 0.35 mm was manufactured. The final cross-sectional shrinkage rate was 28%. As a result of manufacturing the coil spring by minimizing the coil diameter by a method (method B) using a coil manufacturing machine, a coil spring having an outer diameter of 1.75 mm could be manufactured. A 2.05 mm coil spring was also manufactured. After passing a 0.75 mm wire through the inside of a coil spring with an outer diameter of 1.75 mm, both ends of the coil spring are fixed to the grip as shown in FIG. Reduced. When the required coil diameter was 1.45 mm, for example (the coil diameter was not further reduced by the wire in the coil spring), the distance between the grips was adjusted so that the pitch was 1.0 mm. After fixing the grip, heat treatment was performed at an appropriate temperature (about 250 to 600 ° C.), and a desired coil spring shape could be obtained. A 2.05 mm coil spring could be reduced in diameter in a similar manner, but twisted at about 1.75 mm. Here, a coil spring having an outer diameter of 1.75 mm was obtained by primary heat treatment (for example, at 350 ° C. for 10 minutes). After the heat treatment, the grip was further rotated to reduce the diameter, and when heat treatment was performed with the final desired shape, the desired shape memory alloy coil spring shape was obtained accurately.

DESCRIPTION OF SYMBOLS 10 Coil spring 20, 30 Grip 22, 32 Groove 40, 50 Wire 55 Rod-shaped member 60, 70 1st pipe 65, 75 2nd pipe

Claims (15)

Producing a coil spring;
A diameter reduction step of rotating the both ends of the coil spring to give a torsional deformation to reduce the coil diameter;
After the diameter reducing step is finished, a pitch adjusting step of adjusting a pitch of the coil spring by adjusting a distance between both ends of the coil spring;
A heat treatment step of performing shape memory heat treatment on the coil spring that has undergone the pitch adjustment step ;
A method of manufacturing a shape memory alloy coil spring. The diameter reduction step includes:
A fixing step of fixing both ends of the coil spring using two grips;
A rotation stage for rotating the two grips;
The method of manufacturing a shape memory alloy coil spring according to claim 1, comprising:   3. The method of manufacturing a shape memory alloy coil spring according to claim 2, wherein the grip has a cylindrical shape or a columnar shape in which a spiral groove is formed on an outer peripheral surface.   The method of manufacturing a shape memory alloy coil spring according to claim 3, wherein in the fixing step, both ends of the coil spring are inserted and fixed in the spiral groove. The method for manufacturing a shape memory alloy coil spring according to claim 1 , wherein the diameter reduction step and the heat treatment step are repeatedly performed a plurality of times. A fixing stage for fixing both ends of the coil spring using two grips;
A diameter reduction step of rotating the two grips in opposite directions to twist the coil spring to reduce the coil diameter;
After the diameter reducing step is finished, a pitch adjusting step of adjusting a pitch of the coil spring by adjusting a distance between both ends of the coil spring;
A heat treatment step of performing shape memory heat treatment on the coil spring that has undergone the pitch adjustment step ;
A method of manufacturing a shape memory alloy coil spring. A spiral groove into which both ends of the coil spring are inserted is formed on the outer peripheral surface of the grip,
The method of manufacturing a shape memory alloy coil spring according to claim 6 , wherein in the fixing step, both ends of the coil spring are inserted and fixed in the spiral groove. The method for manufacturing a coil spring according to claim 6 or 7 , wherein the diameter reduction step, the pitch adjustment step, and the heat treatment step are repeatedly performed a plurality of times. A fixing step of inserting both ends of the coil spring into the first pipe and inserting a wedge-shaped second pipe between the first pipe and the coil spring to fix the both ends of the coil spring;
Reducing the diameter of the coil by rotating the first pipe to give a torsional deformation to the coil spring;
A pitch adjusting step of adjusting a pitch of the coil spring by adjusting a distance between both ends of the coil spring after the diameter reducing step is completed;
A heat treatment step of performing shape memory heat treatment on the coil spring that has undergone the pitch adjustment step ;
A method of manufacturing a shape memory alloy coil spring. 10. The method of manufacturing a shape memory alloy coil spring according to claim 9 , wherein the diameter reducing step, the pitch adjusting step, and the heat treatment step are repeatedly performed a plurality of times. A fixing stage for fixing both ends of the coil spring using two grips;
Inserting a straight wire or a rod-shaped member into the coil spring;
A diameter reduction step of rotating the two grips in opposite directions to torsionally deform the coil spring to reduce the coil diameter;
A pitch adjusting step of adjusting a pitch of the coil spring by adjusting a distance between both ends of the coil spring after the diameter reducing step is completed;
A heat treatment step of performing shape memory heat treatment on the coil spring that has undergone the pitch adjustment step ;
A method of manufacturing a shape memory alloy coil spring. The method of manufacturing a shape memory alloy coil spring according to claim 11 , wherein a plurality of the straight wires are arranged inside the coil spring. The straight wire in order to determine the diameter range of the coil spring in said reduced diameter step, claim 11, characterized in that is positioned on a circumference having a diameter corresponding to the final inner diameter of the coil spring or A manufacturing method of the shape memory alloy coil spring according to 12 . A spiral groove into which both ends of the coil spring are inserted is formed on the outer peripheral surface of the grip,
The method of manufacturing a shape memory alloy coil spring according to any one of claims 11 to 13 , wherein in the fixing step, both ends of the coil spring are inserted and fixed in the spiral groove. The method of manufacturing a shape memory alloy coil spring according to claim 11, wherein the diameter reduction step, the pitch adjustment step, and the heat treatment step are repeatedly performed a plurality of times.

Images